Method and apparatus for forming undercut corrugations in sheet metal

ABSTRACT

A metal sheet or band is clamped betweed spaced pairs of clamps, movable toward and away from each other, at points spaced apart a distance equal to the width of the sheet required to define an undercut corrugation to be formed. A forming die having an enlarged head, such as a circular cross-section head, and a narrow neck, such as a rectangular neck, extending from the head, is movable perpendicularly to the plane of the sheet centrally between the pairs of clamps to engage and deform the sheet while the pairs of clamps are moved toward each other to wrap the sheet closely around the head and neck of the die to form the undercut corrugation. A second die may be provided to move in opposition to the first die to press the metal sheet against the top of the head of the first die. After formation of the undercut corrugation, the pairs of closed clamps are retracted relative to each other to provide clearance for retraction of the die head through the narrow undercut portion of the formed corrugation. The clamps may then be released, or they may be brought toward each other until they are spaced apart a distance equal to the thickness of the narrow part of the undercut corrugation. Stops may be provided to limit the movement of the clamps relative to each other.

Oct. 1, 1974 METHOD AND APPARATUS FOR FORMING UNDERCUT CORRUGATIONS IN SHEET METAL Inventor: Edsger Wybe Van Dijk, Albert Neuhuysstraat 25, Utrecht, Netherlands Filed: Mar. 13, 1973 Appl. No.: 340,874

[30] Foreign Application Priority Data [56] References Cited UNITED STATES PATENTS 3/1892 Singer 72/401 11/1928 Gray 72/403 3,461,711 8/1969 Ogilvie 72/383 3,768,294 10/1973 Van Dijk 72/309 FORElGN PATENTS OR APPLICATIONS 177,308 1/1954 Austria 72/403 79,261 2/1932 Sweden 72/403 Primary Examiner-C. W. Lanham Assistant ExaminerM. J. Keenan Attorney, Agent, or FirmBlum, Moscovitz, Friedman & Kaplan 5 7] ABSTRACT A metal sheet or band is clamped betweed'spaced pairs of clamps, movable toward and away from each other, at points spaced apart a distance equal to the width of the sheet required to define an undercut corrugation to be formed. A forming die having an enlarged head, such as a circular cross-section head, and a narrow neck, such as a rectangular neck, extending from the head, is movable perpendicularly to the plane of the sheet centrally between the pairs of clamps to engage and deform the sheet while the pairs of clamps are moved toward each other to wrap the sheet closely around the head and neck of the die to form the undercut corrugation. A second die may be provided to move in opposition to the first die to press the metal sheet against the top of the head of the first die. After formation of the undercut corrugation, the pairs of closed clamps are retracted relative to each other to provide clearance for retraction of the die head through the narrow undercut portion of the formed corrugation. The clamps may then be released, or they may be brought toward each other until they are spaced apart a distance equal to the thickness of the narrow part of the undercut corrugation. Stops may be provided to limit the movement of the clamps relative to each other.

7 Claims, 10 Drawing Figures PAFENIEnum nan sum 10; 2

METHOD AND APPARATUS FOR FORMING UNDERCUT CORRUGATIONS IN SHEET METAL FIELD AND BACKGROUND OF THE INVENTION The invention is directed to the manufacturing or forming of undercut corrugations in a metal sheet or band and, more particularly, to a novel and improved method of and apparatus for effecting such formation.

In a known apparatus for forming undercut corrugations in a metal sheet or band, two pairs of clamps are arranged in a frame to be movable horizontally relative to each other while clamping therebetween a piece of sheet metal. At the same time, as the clamps are moved toward each other, a forming die, positioned between the pairs of clamps and beneath the sheet material, is moved upwardly, with the motions of the clamps and of the forming die being coordinated in such a way that the sheet is folded against the forming die without shifting relative to the die. Such an apparatus is disclosed, for example, in Netherlands Pat. No. 132,181. In the known apparatus, the forming die is then retracted to its original position while the clamps remain stationary, after which the clamps, with the corrugation between them, are moved further toward each other.

With the known procedure, it is indeed possible to form a manifold of several undercut corrugations. However, if the material to be corrugated is not entirely homogeneous, either in thickness or in its mechanical properties, exactly the same corrugation is not always obtained, and identical corrugations are often required.

SUMMARY OF THE INVENTION gations which can be formed and, on the other hand,

to decrease the dependence of reproducible results on the homogenity of the material. In accordance with the invention, the forming part of the forming die is made in such a way that, by folding of the sheet material against the forming die, an undercut corrugation is formed. With springy material, the undercut corrugation may be released by loosening the clamps, moving them outward a slight distance from their middle position, and then retracting the forming die forcibly, whereby the deformation of the formed corrugation, caused by the passing of the widest part of the forming die through the narrowest part of the corrugation, is compensated by springback of the force of the opened corrugation.

In accordance with the invention, the forming die may also be withdrawn from the corrugation by maintaining the clamps closed and moving them sufficiently far apart that the forming die may be pulled back freely through the resultant opened corrugation. The undercut corrugation, already shaped, is thereby partly unfolded. From experiments, however, it has been determined that the deformation by the original formation has been such, in many cases, that in moving the clamps together again, while clamping the sheet, the original corrugation is restored. Although it is not always necessary, a suitable counterdie beam, as known from the art, may be used.

An object of the invention is to provide a novel method of forming a series of undercut corrugations in sheet metal.

Another object of the invention is to provide an improved apparatus for forming a series of undercut corrugations in sheet metal.

A further object of the invention is to provide such a method and apparatus operable to form identical corrugations in sheet metal and independent of whether or not the material is completely homogeneous either in thickness or in mechanical properties.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combinations of elements and arrangement of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a somewhat schematic perspective view of apparatus embodying the invention; and

FIGS. 2 through 10 are somewhat schematic vertical sectional views along the line 2-2 of FIG. 1 and illustrating the different phases of a working cycle.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, the metal sheet to be corrugated is indicated at 15, with the corrugation to be formed being indicated, as in FIG. 10, at 30. The'apparatus includes clamps l2, l2 and 13, 13 which are arranged to be moved substantially horizontally toward and away from each other. Motions of clamps 12 and 13 away from each other, or away from the center of the apparatus, are limited by adjustable stops l6 and 16', it being noted that the stops 16' are substantially longer than the stops 16. Stops 18 limit movement of clamps l2 and 13 toward each other, and are adapted to the ultimately required corrugation. Stops 18 may be omitted if the required corrugation requires that, in the last folding operation, as shown in FIGS. 6 and 7, the clamps l2 and 13 are moved as close to each other as possible. Adjustable stops 17 are provided and, in the phase of the apparatus shown in FIGS. 1 and 2, are positioned directly beneath clamps 12 and 13.

The undercut corrugation is arranged to be formed by a lower die, generally indicated at 20, including, in the illustrated example, a circular cross-section head 21 and a narrow neck 22, neck 22 being received in a groove 24 in a die support 23, so that lower die 20 is interchangeable when different shaped undercut corrugations are to be formed. An upper die 25 is provided, in the particular example shown in the drawings, to cooperate with lower die 20, and includes a die part 26, having a concave lower edge, inserted into a groove 28 in a die support 27, so that die part 26 is also interchangeable with other die parts. Such interchangeability allows the use of various shapes of dies in the respective die holders 23 and 27 in accordance with the particular shape of the undercut corrugation to be formed in metal sheet 15.

In the phase of the operation indicated in FIGS. 1 and 2, metal sheet has been clamped by the pairs of clamps 12 and 13 while the latter are in engagement with the outer limit stops l6 and 16 respectively. Clamps 12 and 13 maintain sheet 15 pressed while the clamps are moved toward each other. During such mvoement, forming die is moved upwardly to engage and deform sheet 15 by wrapping of the sheet metal around the head 21 and pressing of the sheet metal against the neck 22, of die 20. At the same time, if counterdie 25 is provided, it presses against the sheet metal engaged with the upper portion of head 21. The parts thus obtain the state shown in FIG. 3.

At this time, stops 17, 17 initially positioned under clamps 12 and 13 move upwardly to limit the retraction motion of clamps l2 and 13, the parts now occupying the position shown in FIG. 4. Clamps l2 and 13 are then retracted until they engage the stops 17, as shown in FIG. 5. Due to this retraction of the closed clamps 12 and 13, the sheet material hitherto folded around forming die 20 is partially unfolded, also as shown in FIG. 5. The adjustment of stops 17 must be such that, when clamps 12 and 13 engage these stops, the head 21 of forming die 20 can be retracted vertically through the resultant opening in the undercut corrugation 30.

When forming die 20 has been retracted, the parts have the position as shown in FIG. 6. The formed, and afterwards partly unfolded sheet material 15, has been deformed permanently by the first forming action in such a way that, when clamps 12 and 13 are again moved toward each other, as shown in FIG. 7, the undercut corrugation assumes its originally formed shape. Such inward movement of clamps 12 and 13 toward each other is limited by the stops 18.

The shaped corrugation must now be freed. For this purpose, the upper clamps 12 and 13, of the respective pairs of clamps, are displaced a slight distance upwardly, carrying with them the counterdie 25. Stops 17, at the same time, are returned to their retracted position. It is also possible to lower the lower clamps 12 and 13, of the respective clamp pairs, a small amount.

After this operation, clamps 12 and 13 are retracted horizontally to their outer limiting position in which they engage the stops l6 and 16', respectively, and are aligned over the stops 17. At the same time, the upper clamp 13 is raised a sufficient amount, as shown in FIG. 9, so that the shaped corrugation 30 can be shifted to the right beneath the upper die 13. Sheet material 15 is moved to the right through the distance required or performed by the usual feeding apparatus, which has not been shown, so that the parts attain the position shown in FIG. 10.

With the parts having the position shown in FIG. 10, the cycle is repeated by engaging clamps 12 and 13 with the sheet 15 and operating the dies 20 and 25 to form a new corrugation, with the initial step being the same as illustrated in FIGS. 1 and 2.

In the illustrated embodiment of the invention, the counterdie 25 is used. Very often this is not necessary, and it is not really necessary in the illustrated embodiment. For example, if the forming part or head 21 of forming die 20 is designed with an elliptical crosssection having the longer axis extending horizontally, the same ultimate corrugation would be obtained.

As a matter of practice, many constructional variations are possible with respect to the schematically illustrated embodiment. All of them have in common that the forming part or head of the forming die has, under its widest part, a narrower part or neck 22 whereby, upon folding of the sheet material around the head, there is shaped at all times an undercut corrugation.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in carrying out the above method and in the construction set forth without departing from the spirit or scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific fea tures of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed is:

1. A method of forming a series of undercut corrugations in a metal sheet or band comprising the steps of clamping a sheet between spaced pairs of clamps, movable toward and away from each other, at points spaced apart a distance equal to the width of the sheet defining the undercut corrugation to be formed; moving a forming die, having an enlarged head and a narrow neck, perpendicular to the plane of the sheet centrally between the pairs of clamps to engage and deform the sheet while moving the pairs of clamps toward each other to wrap the sheet around the head and neck of the die to form the undercut corrugation; and thereafter opening the undercut corrugation an amount sufficient to provide clearance for retraction of the die head through the undercut portion of the formed undercut corrugation.

2. A method of forming a series of undercut corrugations in a metal sheet or band, as claimed in claim 1, in which, when the metal sheet or band is springy, opening of the undercut corrugation is effected by retraction of the forming die.

3. A method of forming a series of undercut corrugations in a metal sheet or band, as claimed in claim 1, in which opening of the undercut corrugation is effected by withdrawing the pairs of closed clamps a distance sufficient to provide clearance for retraction of the die head through the undercut portion of the formed undercut corrugation.

4. A method of forming a series of undercut corrugations in a metal sheet or band, as claimed in claim 3, including, following such withdrawal of said clamps, advancing the clamps toward each other to restore the undercut corrugation to its initial shape.

5. A method of forming a series of undercut corrugations in a metal sheet or band, as claimed in claim 1, including applying a counterdie against the sheet wrapped around the head of the forming die.

6. A corrugating station for forming a series of undercut corrugations in a sheet metal or band, comprising in combination, means for intermittently moving said sheet metal or band in a first direction into a position to be corrugated, a forming die having an enlarged continuous cross-sectioned head terminating in a narrow neck, said narrow' neck being mounted for movement perpendicular to the plane of said sheet, a counter die movable in opposition to and alignment with said forming die and having a surface cross-sectioned to mate with said forming die when said surface is moved in contact with said sheet portion wrapped around said forming die by the perpendicular movement of said forming die into engagement with said sheet, and spaced pairs of clamps on each side of said forming die, said clamp pairs being adapted to be moved toward said forming die to form said corrugation and away from said forming die after said corrugation is formed, and means for moving one of said clamps of said clamp pair downstream of the direction of intermittent movement of said sheet metal and on the same side of the sheet metal as said counter die, and said counter die, away from said sheet after said clamp pairs have been moved away from said counter die prior to the intermitformed under cut corrugation. 

1. A method of forming a series of undercut corrugations in a metal sheet or band comprising the steps of clamping a sheet between spaced pairs of clamps, movable toward and away from each other, at points spaced apart a distance equal to the width of the sheet defining the undercut corrugation to be formed; moving a forming die, having an enlarged head and a narrow neck, perpendicular to the plane of the sheet centrally between the pairs of clamps to engage and deform the sheet while moving the pairs of clamps toward each other to wrap the sheet around the head and neck of the die to form the undercut corrugation; and thereafter opening the undercut corrugation an amount sufficient to provide clearance for retraction of the die head through the undercut portion of the formed undercut corrugation.
 2. A method of forming a series of undercut corrugations in a metal sheet or band, as claimed in claim 1, in which, when the metal sheet or band is springy, opening of the undercut corrugation is effected by retraction of the forming die.
 3. A method of forming a series of undercut corrugations in a metal sheet or band, as claimed in claim 1, in which opening of the undercut corrugation is effected by withdrawing the pairs of closed clamps a distance sufficient to provide clearance for retraction of the die head through the undercut portion of the formed undercut corrugation.
 4. A method of forming a series of undercut corrugations in a metal sheet or band, as claimed in claim 3, including, following such withdrawal of said clamps, advancing the clamps toward each other to restore the undercut corrugation to its initial shape.
 5. A method of forming a series of undercut corrugations in a metal sheet or band, as claimed in claim 1, including applying a counterdie against the sheet wrapped around the head of the forming die.
 6. A corrugating station for forming a series of undercut corrugations in a sheet metal or band, comprising in combination, means for intermittently moving said sheet metal or band in a first direction into a position to be corrugated, a forming die having an enlarged continuous cross-sectioned head terminating in a narrow neck, said narrow neck being mounted for movement perpendicular to the plane of said sheet, a counter die movable in opposition to and alignment with said forming die and having a surface cross-sectioned to mate with said forming die when said surface is moved in contact with said sheet portion wrapped around said forming die by the perpendicular movement of said forming die into engagement with said sheet, and spaced pairs of clamps on each side of said forming die, said clamp pairs being adapted to be moved toward said forming die to form said corrugation and away from said forming die after said corrugation is formed, and means for moving one of said clamps of said clamp pair downstream of the direction of intermittent movement of said sheet metal and on the same side of the sheet metal as said counter die, and said counter die, away from said sheet after said clamp pairs have been moved away from said counter die prior to the intermittent movement of said sheet.
 7. A corrugating station as claimed in claim 6 and including outer stops for limiting the movement of said clamp pairs away from each other after said corrugation has been formed and intermediate stops selectively positioned in the path of said clamp pairs being displaced away from each other to limit the retracting movement of said clamps to a distance sufficient to provide an opening of the formed corrugation and thereby allow said forming die to be removed from said corrugation through the undercut portion of the formed under cut corrugation. 